1. Field of the Invention
The present invention pertains to ultrasonic motors used for timepieces, cameras, printers, memory devices and so on. More particularly, the present invention pertains to an ultrasonic motor with reduced vibration inefficiency to more efficiently transmit a drive force to a moving member;
2. Description of the Related Art
A conventional ultrasonic motor utilizes, as power to move a moving member, elliptic vibration that is a resultant vibration of expansion-and-contraction vibration and flex vibration caused on a piezoelectric element applied by a drive signal such as an alternating current voltage. Recently, attention has been drawn to ultrasonic motors particularly in the field of micro-mechanics, because of their high electric-to-mechanical energy conversion efficiency.
A conventional ultrasonic motor generally has a piezoelectric element as a drive power source, a signal transmission means for transmitting drive signals to the piezoelectric element, and an elastic member for pressure-contacting the piezoelectric element with the moving member to efficiently transmit drive power to the moving member.
Where such a ultrasonic motor is installed on a circuit board, such as a printed circuit board, it is held on the circuit board by a support member that holds the piezoelectric element of the ultrasonic motor.
However, it is necessary for the conventional ultrasonic motor to provide the piezoelectric element with a signal transmission part, such as conductor wires, to apply a drive signal to the piezoelectric element. Loss occurs of the expansion-and-contraction vibration and flex vibration through both the support member and the signal transmission part. In addition loss of the expansion-and-contraction vibration and flex vibration also occurs through the elastic member.
As a result, a conventional ultrasonic motor does not efficiently transmit drive force to the moving member, thus impairing the electric-to-mechanical energy conversion.
Further, mounting a plurality of elements on the piezoelectric element prevents size reduction for the ultrasonic motor and decreases the reliability of the motor.
Accordingly, it is an object of the present invention to provide an ultrasonic motor with reduced loss of the drive force produced on a piezoelectric element so as to efficiently transmit the drive force to a moving member, and wherein size reduction and improvement in reliability are achieved.